Out of curiousity, I wanted to take a look at a vertical market that is dominated by three players. Looking at Office Supplies online the players are Staples.com, OfficeDepot.com and OfficeMax.com. Revenue between those three account for over 98% of total e-commerce revenue for that vertical market. The 2005 (sorry, working of an old Internet Retailer book) revenue is as follows:

Basically, Staples.com and OfficeDepot.com were the same with OfficeMax.com pulling in a respectable $2.6B, yes BILLION. So that was 2005. Now lets look at what is going on now. Check out the compete.com chart below which includes the most current visitor data for October:

What is cool is that you can download the data you can see the 12 months prior visitor data which I downloaded to Excel below:

Okay, a couple of things stand out.
Overall visitors to the three combined are down 9% vs. October last year.
OfficeMax.com traffic is down over 18% vs. October Last Year
OfficeDepot gained 2% market share in October of this year.
OfficeMax.com makes more money per visitor than Staples.com and OfficeDepot.com
November and December visitors last year were all +50% vs. October last year.
So the questions are:
Will OfficeMax have below expected holiday sales?
Will OfficeDepot.com overtake Staples.com?
My educated guess is that holiday sales at the big office supply sites are going to struggle vs. last year. Look for them to promote more in the upcoming months due to the current downturn in visitors to their sites. OfficeMax.com has a big hill to climb and needs to push hard quickly.